This invention relates to fuel injectors, and more particularly, to fuel injectors having a single disc which generates turbulence at the metering orifices.
Fuel injectors are commonly employed in internal combustion engines to provide precise metering of fuel for introduction into each combustion chamber. Additionally, the fuel injector atomizes the fuel during injection, breaking the fuel into a large number of very small particles, increasing the surface area of the fuel being injected and allowing the oxidizer, typically ambient air, to more thoroughly mix with the fuel prior to combustion. The precise metering and atomization of the fuel reduces combustion emissions and increases the fuel efficiency of the engine.
An electro-magnetic fuel injector typically utilizes a solenoid assembly to supply an actuating force to a fuel metering valve. Typically, the fuel metering valve is a plunger style needle valve which reciprocates between a closed position, when the needle is seated in a valve seat along a sealing diameter to prevent fuel from escaping through a metering orifice disc into the combustion chamber, and an open position, where the needle is lifted from the valve seat, allowing fuel to discharge through the metering orifice for introduction into the combustion chamber.
Typically, the metering orifice disc includes a plurality of metering orifice openings which are directly below the needle and inward of the sealing diameter. This approach relies on a precise control of the distance between the end of the needle and the upstream surface of the metering orifice disc. Variations in needle geometry, sealing diameter, and lift of the needle can cause this critical dimension to change. Another approach to maintaining precise control of this dimension uses a multi-disc concept. However, this approach has the added complexity of orientation, delamination, and part handling.
It would be beneficial to develop a fuel injector in which a controlled precise geometry is created at the downstream surface of the valve seat to generate desired turbulence at the metering orifice openings.
Briefly, the present invention is a fuel injector comprising a housing, a valve seat, a metering orifice disc and a needle. The housing has an inlet, an outlet and a longitudinal axis extending therethrough. The valve seat is disposed proximate the outlet. The valve seat includes a passage having a sealing surface and an orifice. The metering orifice disc is located at the outlet and includes a plurality of metering openings extending therethrough. The needle is reciprocally located within the housing along the longitudinal axis between a first position wherein the needle is displaced from the valve seat, allowing fuel flow past the needle, and a second position wherein the needle is biased against the valve seat, precluding fuel flow past the needle. A controlled velocity channel is formed between the valve seat and the metering orifice disc. The controlled velocity channel extends outwardly from the orifice to the plurality of metering openings.
Additionally, the present invention is a method of generating turbulence in a fuel flow through a fuel injector. The method includes providing a fuel flow under pressure to the fuel injector. A valve in the fuel injector is opened and the pressurized fuel flows past the valve and into a fuel chamber. The fuel flow is directed at an initial velocity from the fuel chamber into a controlled velocity channel formed by a valve seat and a metering orifice disc. The controlled velocity channel tapers from a first height at an upstream end of the controlled velocity channel to a second height at a downstream end of the controlled velocity channel. The second height is smaller than the first height. The fuel maintains a generally controlled velocity through the controlled velocity channel. The final velocity is higher than the initial velocity and generates turbulence within the fuel flow. The fuel flow is then directed through at least one orifice opening downstream of the controlled velocity channel and out of the fuel injector.